1. Technical Field
The present invention relates to a submersible pump and a submersible pump system for a marine structure, such as a ship or a semi-submersible unit. The invention further relates to an arrangement for hydraulic drive of the submersible pump and to a semi-submersible unit comprising the submersible pump system. The described submersible pump may also be used in other appliances in which a liquid is to be pumped using a submersible pump.
2. Background of the Invention
A marine structure, such as a ship or a semi-submersible unit, uses sea water for a number of purposes for example in the ballast system, in the fire fight system and for sea water cooling systems. Generally, these systems comprise a plurality of tanks, which are adapted to be filled with sea water, i.e. water ambient of the marine structure, through a sea water system. The sea water system generally comprises several submersible pumps, so called primary pumps, for pumping up sea water above the sea water level to the marine structure. It further comprises tubes for transport of the sea water to tanks and/or to connecting tubes having booster pumps for further transport of sea water to the different users of the sea water system.
The primary pumps are sometimes subjected to service or need to be exchanged. At these occasions the pump has to be lifted up from its submerged pumping location to a service location above the sea water level. The transportation of the primary pump between a pumping location and a service location is a hazardous operation. There is a risk that a pump is unintentionally dropped due to incorrect handling of the lifting facilities and/or defects in the material of the lifting facilities. Often, the environment where these pumps are installed is exposed to difficult and extreme weather conditions which also may contribute to the risk scenario. A free falling pump may cause severe damages not only to the pump but also to equipment or installations on the marine structure or to human beings working there. Further, the dropping of a pump may also cause damages to sub-sea installations on the sea bed. Dropping a pump may also lead to time consuming and very costly reparation actions.
In view of the above, it may be realized that there is a need for improvements in the field of submersible pump for marine structures.